Secondary battery including insulating member with grooves

ABSTRACT

A conductive member ( 61 ) is disposed near a side of the sealing plate ( 2 ) facing the inside of a battery with a first insulating member ( 10 ) disposed therebetween. The conductive member ( 61 ) has a conductive-member opening portion ( 61   f ) at a side facing the electrode assembly. An inserting portion ( 7   b ) of a positive electrode terminal ( 7 ) is inserted through a third terminal-receiving hole ( 61   c ) in the conductive member ( 61 ) and connected to the conductive member ( 61 ). The conductive-member opening portion ( 61   f ) of the conductive member ( 61 ) is sealed by a deformation plate ( 62 ), and the deformation plate ( 62 ) is connected to a first positive-electrode current collector ( 6   a ), which is electrically connected to positive electrode plates. The conductive member ( 61 ) includes a pressing projection ( 61   e ) that projects toward the first insulating member ( 10 ) from a portion thereof that faces the first insulating member ( 10 ).

TECHNICAL FIELD

The present invention relates to a secondary battery.

BACKGROUND ART

Driving power sources of, for example, electric vehicles (EVs) andhybrid electric vehicles (HEVs or PHEVs) include secondary batteries,such as alkaline secondary batteries and nonaqueous electrolytesecondary batteries.

A rectangular secondary battery includes a battery case constituted by arectangular exterior body having the shape of a tube with an opening anda bottom and a sealing plate that seals the opening. The battery casecontains an electrode assembly, which includes positive electrodeplates, negative electrode plates, and separators, together with anelectrolyte. A positive electrode terminal and a negative electrodeterminal are attached to the sealing plate. The positive electrodeterminal is electrically connected to the positive electrode plates by apositive-electrode current collector, and the negative electrodeterminal is electrically connected to the negative electrode plates by anegative-electrode current collector.

A rectangular secondary battery including a current interruptionmechanism has been proposed (see PTL 1 below). The current interruptionmechanism is activated and breaks a conductive path between an electrodeassembly and a terminal to interrupt current when a pressure in abattery case reaches or exceeds a predetermined value due to, forexample, overcharging.

CITATION LIST Patent Literature

PTL 1: Japanese Published Unexamined Patent Application No. 2013-157099

SUMMARY OF INVENTION Technical Problem

A secondary battery including a current interruption mechanism is highlyreliable in terms of, for example, protection against overcharging.However, secondary batteries with higher reliabilities are desired.

The main object of the present invention is to provide ahigh-reliability secondary battery including a current interruptionmechanism having an activation pressure with increased stability.

Solution to Problem

A secondary battery according to an embodiment of the present inventionincludes

an electrode assembly including a positive electrode plate and anegative electrode plate;

an exterior body having an opening and containing the electrodeassembly;

a sealing plate that seals the opening;

a conductive member having an opening portion at a side facing theelectrode assembly and disposed near a side of the sealing plate facingthe electrode assembly such that a first insulating member is disposedbetween the sealing plate and the conductive member;

a deformation plate that seals the opening portion and that is deformedin response to an increase in a pressure in the exterior body;

a current collecting member that electrically connects the positiveelectrode plate or the negative electrode plate to the deformationplate; and

a terminal that is electrically connected to the positive electrodeplate or the negative electrode plate via the current collecting member,the deformation plate, and the conductive member.

The terminal is inserted through a terminal attachment hole in thesealing plate, a terminal-receiving hole in the first insulating member,and a terminal-receiving hole in the conductive member and connected tothe conductive member.

At least one of the conductive member and the sealing plate has apressing projection that projects toward the first insulating memberfrom a portion thereof that faces the first insulating member.

A conductive path between the positive electrode plate and the terminalor between the negative electrode plate and the terminal is broken inresponse to a deformation of the deformation plate.

Preferably, the terminal is inserted in the terminal-receiving hole inthe conductive member, which is a component of a current interruptionmechanism, and connected to the conductive member. According to such aconfiguration, a secondary battery including a current interruptionmechanism with increased reliability can be easily provided. However,the inventors have found that the secondary battery having such aconfiguration has a problem describe below, and there is room forimprovement.

A secondary battery in which a terminal and a conductive member areseparate components and in which the terminal is inserted in aterminal-receiving hole in the conductive member and connected to theconductive member may cause the following phenomenon. That is, when alarge amount of gas is generated in the electrode assembly as a resultof abnormal operation of the secondary battery, there is a risk that thegenerated gas will pass through a gap between the sealing plate and thefirst insulating member or a gap between the first insulating member andthe conductive member and flow toward a connecting portion between theconductive member and the terminal. Then, the gas may leak into thespace defined by the conductive member and the deformation plate througha gap between the conductive member and the terminal. Such gas leakagemay cause a delay in the activation of the current interruptionmechanism.

The secondary battery according to the embodiment of the presentinvention is configured such that at least one of the conductive memberand the sealing plate has the pressing projection at the position wherethe pressing projection faces the first insulating member. Therefore,the first insulating member disposed between the conductive member andthe sealing plate is more strongly pressed by the pressing projection,and gas can be prevented from flowing toward the connecting portionbetween the conductive member and the terminal. As a result, gas in theregion around the electrode assembly does not leak into the spacedefined by the conductive member and the deformation plate. As a result,a delay in the activation of the current interruption mechanism can bereliably prevented.

There is no particular limitation regarding the method for connectingthe terminal and the conductive member. The terminal is preferablyinserted into the conductive member and crimped onto the conductivemember. In addition, the crimped portion of the terminal is preferablyconnected to the conductive member by welding. The terminal may beinserted into the conductive member and connected to the conductivemember by welding.

Advantageous Effects of Invention

The present invention provides a secondary battery with increasedreliability.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of a secondary battery according to anembodiment.

FIG. 2 is a sectional view taken along line in FIG. 1.

FIG. 3 is a plan view of a positive electrode plate according to theembodiment.

FIG. 4 is a plan view of a negative electrode plate according to theembodiment.

FIG. 5 is a plan view of an electrode assembly element according to theembodiment.

FIG. 6 is a perspective view illustrating a positive electrode terminal,an outer insulating member, a sealing plate, a first insulating member,and a conductive member.

FIG. 7 is a bottom view of the sealing plate to which components areattached.

FIG. 8A is a sectional view taken along line VIIIA-VIIIA in FIG. 7, FIG.8B is a sectional view taken along line VIIIB-VIIIB in FIG. 7, and FIG.8C is a sectional view taken along line VIIIC-VIIIC in FIG. 7.

FIG. 9 is a perspective view of a deformation plate.

FIG. 10A is a perspective view of a first positive-electrode currentcollector and a second insulating member before assembly, FIG. 10B is aperspective view of the first positive-electrode current collector andthe second insulating member after assembly, and FIG. 10C is aperspective view of the first positive-electrode current collector andthe second insulating member that have been fixed together.

FIG. 11 is an enlarged view of a part of FIG. 8A including a connectingportion between the deformation plate and the first positive-electrodecurrent collector.

FIG. 12 is a perspective view of the sealing plate to which componentsare attached.

FIG. 13 is a sectional view of a part including a negative electrodeterminal taken in a long-side direction of the scaling plate.

FIG. 14 illustrates a method for attaching tabs to current collectingmembers.

FIG. 15 is a perspective view of the sealing plate and a cover.

FIG. 16A illustrates a state before the cover is attached to the firstinsulating member and the second insulating member, and FIG. 16Billustrates a state after the cover is attached to the first insulatingmember and the second insulating member.

FIG. 17A is a sectional view of a part including the positive electrodeterminal after the cover is attached, taken in the long-side directionof the sealing plate, and FIG. 17B is a sectional view of a partincluding a connecting portion between the cover and the firstinsulating member, taken in a short-side direction of the sealing plate.

FIG. 18 is an enlarged view of a part of FIG. 8A including a connectingportion between the positive electrode terminal and the conductivemember.

FIG. 19A illustrates a state before a cover of a secondary batteryaccording to a modification is attached to a first insulating member anda second insulating member, and FIG. 19B illustrates a state after thecover of the secondary battery according to the modification is attachedto the first insulating member and the second insulating member.

FIG. 20 is a sectional view of a part including a current interruptionmechanism of a secondary battery according to a modification.

DESCRIPTION OF EMBODIMENTS

The structure of a rectangular secondary battery 20, which is asecondary battery according to an embodiment, will now be described. Thepresent invention is not limited to the embodiment.

FIG. 1 is a perspective view of the rectangular secondary battery 20.FIG. 2 is a sectional view taken along line II-II in FIG. 1. Asillustrated in FIGS. 1 and 2, the rectangular secondary battery 20includes a battery case 100 constituted by a rectangular exterior body 1having the shape of a rectangular tube with an opening and a bottom anda sealing plate 2 that seals the opening in the rectangular exteriorbody 1. The rectangular exterior body 1 and the sealing plate 2 are eachpreferably made of a metal, for example, aluminum or an aluminum alloy.The rectangular exterior body 1 contains an electrode assembly 3together with an electrolyte. The electrode assembly 3 has a stackedstructure in which positive electrode plates and negative electrodeplates are stacked together with separators interposed therebetween. Aninsulating sheet 14 made of a resin is disposed between the electrodeassembly 3 and the rectangular exterior body 1.

Positive-electrode tabs 40 and negative-electrode tabs 50 are providedat an end of the electrode assembly 3 that is adjacent to the sealingplate 2. The positive-electrode tabs 40 are electrically connected to apositive electrode terminal 7 via a second positive-electrode currentcollector 6 b and a first positive-electrode current collector 6 a. Thenegative-electrode tabs 50 are electrically connected to a negativeelectrode terminal 9 via a second negative-electrode current collector 8b and a first negative-electrode current collector 8 a. The firstpositive-electrode current collector 6 a and the secondpositive-electrode current collector 6 b constitute a positive-electrodecurrent collecting member 6. The first negative-electrode currentcollector 8 a and the second negative-electrode current collector 8 bconstitute a negative-electrode current collecting member 8. Thepositive-electrode current collecting member 6 may instead beconstituted by a single component. Also, the negative-electrode currentcollecting member 8 may instead be constituted by a single component.

The positive electrode terminal 7 is fixed to the sealing plate 2 withan outer insulating member 11 made of a resin interposed therebetween.The negative electrode terminal 9 is fixed to the sealing plate 2 withan outer insulating member 13 made of a resin interposed therebetween.The positive electrode terminal 7 is preferably made of a metal, morepreferably aluminum or an aluminum alloy. The negative electrodeterminal 9 is preferably made of a metal, more preferably copper or acopper alloy.

A conductive path between the positive electrode terminal 7 and thepositive electrode plates is preferably provided with a currentinterruption mechanism 60 that is activated to break the conductive pathbetween the positive electrode terminal 7 and the positive electrodeplates when a pressure in the battery case 100 reaches or exceeds apredetermined value. A conductive path between the negative electrodeterminal 9 and the negative electrode plates may also be provided with acurrent interruption mechanism.

The sealing plate 2 is provided with a gas discharge valve 17 thatbreaks to enable gas in the battery case 100 to be discharged out of thebattery case 100 when the pressure in the battery case 100 reaches orexceeds a predetermined value. The activating pressure of the gasdischarge valve 17 is set to a pressure higher than the activatingpressure of the current interruption mechanism 60.

The sealing plate 2 has an electrolyte introduction hole 15. Theelectrolyte introduction hole 15 is sealed by a sealing plug 16 afterthe electrolyte is introduced into the battery case 100 through theelectrolyte introduction hole 15. The sealing plug 16 is preferably ablind rivet.

A method for manufacturing the rectangular secondary battery 20 andcomponents of the rectangular secondary battery 20 will now be describedin detail.

[Production of Positive Electrode Plate]A positive electrode slurrycontaining a lithium nickel cobalt manganese composite oxide as apositive electrode active material, polyvinylidene fluoride (PVdF) as abinder, a carbon material as a conductive agent, andN-methyl-2-pyrrolidone (NMP) as a dispersion medium is prepared. Thepositive electrode slurry is applied to both sides of a rectangularpiece of aluminum foil having a thickness of 15 μm that serves as apositive electrode core. Then, the positive electrode slurry is dried toremove NMP contained therein so that positive electrode active materialmixture layers are formed on the positive electrode core. After that, acompression process is performed so that the thickness of the positiveelectrode active material mixture layers is reduced to a predeterminedthickness. The thus-obtained positive electrode plate is cut into apredetermined shape.

FIG. 3 is a plan view of a positive electrode plate 4 produced by theabove-described method. As illustrated in FIG. 3, the positive electrodeplate 4 includes a main portion in which positive electrode activematerial mixture layers 4 b are formed on both sides of a positiveelectrode core 4 a having a rectangular shape. The positive electrodecore 4 a projects from an edge of the main portion, and the projectingportion of the positive electrode core 4 a constitutes thepositive-electrode tab 40. The positive-electrode tab 40 may either be aportion of the positive electrode core 4 a, as illustrated in FIG. 3, orbe constituted by another member that is connected to the positiveelectrode core 4 a. The positive-electrode tab 40 preferably includespositive-electrode protecting layers 4 d having an electrical resistancehigher than that of the positive electrode active material mixturelayers 4 b in regions adjacent to the positive electrode active materialmixture layers 4 b.

[Production of Negative Electrode Plate]

A negative electrode slurry containing graphite as a negative electrodeactive material, styrene-butadiene rubber (SBR) as a binder,carboxymethyl cellulose (CMC) as a thickener, and water is prepared. Thenegative electrode slurry is applied to both sides of a rectangularpiece of copper foil having a thickness of 8 μm that serves as anegative electrode core. Then, the negative electrode slurry is dried toremove water contained therein so that negative electrode activematerial mixture layers are formed on the negative electrode core. Afterthat, a compression process is performed so that the thickness of thenegative electrode active material mixture layers is reduced to apredetermined thickness. The thus-obtained negative electrode plate iscut into a predetermined shape.

FIG. 4 is a plan view of a negative electrode plate 5 produced by theabove-described method. As illustrated in FIG. 4, the negative electrodeplate 5 includes a main portion in which negative electrode activematerial mixture layers 5 b are formed on both sides of a negativeelectrode core 5 a having a rectangular shape. The negative electrodecore 5 a projects from an edge of the main portion, and the projectingportion of the negative electrode core 5 a constitutes thenegative-electrode tab 50. The negative-electrode tab 50 may either be aportion of the negative electrode core 5 a, as illustrated in FIG. 4, orbe constituted by another member that is connected to the negativeelectrode core 5 a.

[Production of Electrode Assembly Unit]

Electrode assembly units (3 a and 3 b) having a stacked structure areeach produced by preparing 50 positive electrode plates 4 and 51negative electrode plates 5 produced by the above-described method andstacking them together with rectangular separators made of polyolefininterposed therebetween. As illustrated in FIG. 5, each electrodeassembly element (3 a, 3 b) having a stacked structure is formed so thatthe positive-electrode tabs 40 of the positive electrode plates 4 andthe negative-electrode tabs 50 of the negative electrode plates 5 arestacked together at one end thereof. Each electrode assembly element (3a, 3 b) has separators at the outer sides thereof, and the electrodeplates and the separators may be fastened together in the stacked statewith a piece of tape or the like. Alternatively, the separators may beprovided with adhesive layers so that the separators are bonded to thepositive electrode plates 4 and to the negative electrode plates 5.

The size of the separators in plan view is preferably greater than orequal to that of the negative electrode plates 5. The positive electrodeplates 4 and the negative electrode plates 5 may be stacked togetherafter placing each of the positive electrode plates 4 between twoseparators and thermally welding the separators at the peripheral edgethereof. Each electrode assembly element (3 a, 3 b) may instead beproduced by using an elongated separator and stacking the positiveelectrode plates 4 and the negative electrode plates 5 while fan-foldingthe elongated separator, or by using an elongated separator and stackingthe positive electrode plates 4 and the negative electrode plates 5while winding the elongated separator.

[Attachment of Components to Sealing Plate (Positive Electrode Side)]

A method for attaching the positive electrode terminal 7, the firstpositive-electrode current collector 6 a, and other components to thesealing plate 2 and the structure of a part including the positiveelectrode terminal 7 will be described with reference to FIGS. 2 and 6to 8. FIG. 6 is a perspective view illustrating the positive electrodeterminal 7, the outer insulating member 11, the sealing plate 2, a firstinsulating member 10, and a conductive member 61 before assembly. FIG. 7illustrates the sealing plate 2 to which the components are attachedwhen viewed from the inside of the battery. FIG. 7 does not illustratethe positive-electrode tabs 40 and the negative-electrode tabs 50. FIG.8A is a sectional view of the part including the positive electrodeterminal 7 taken along line VIIIA-VIIIA in FIG. 7. FIG. 8B is asectional view of the part including the positive electrode terminal 7taken along line VIIIB-VIIIB in FIG. 7. FIG. 8C is a sectional view ofthe part including the positive electrode terminal 7 taken along lineVIIIC-VIIIC in FIG. 7.

The outer insulating member 11 is placed on a surface of the sealingplate 2 that faces the outside of the battery in a region including apositive-electrode-terminal attachment hole 2 a. The first insulatingmember 10 and the conductive member 61 are placed on a surface of thesealing plate 2 that faces the inside of the battery in the regionincluding the positive-electrode-terminal attachment hole 2 a. Next, aninserting portion 7 b provided on one side of a flange 7 a of thepositive electrode terminal 7 is inserted through a firstterminal-receiving hole 11 a in the outer insulating member 11, thepositive-electrode-terminal attachment hole 2 a in the sealing plate 2,a second terminal-receiving hole 10 d in the first insulating member 10,and a third terminal-receiving hole 61 c in the conductive member 61.Then, the inserting portion 7 b is crimped onto the conductive member 61at the end thereof. Thus, the positive electrode terminal 7, the outerinsulating member 11, the sealing plate 2, the first insulating member10, and the conductive member 61 are fixed together. When the insertingportion 7 b of the positive electrode terminal 7 is crimped, alarge-diameter portion having an outer diameter greater than the innerdiameter of the third terminal-receiving hole 61 c in the conductivemember 61 is formed at the end of the inserting portion 7 b. The crimpedportion of the inserting portion 7 b of the positive electrode terminal7 is preferably welded to the conductive member 61 by, for example,laser welding. The first insulating member 10 and the outer insulatingmember 11 are each preferably made of a resin.

As illustrated in FIGS. 6 and 8, the first insulating member 10 includesa first-insulating-member main portion 10 a arranged to face the sealingplate 2. A pair of first side walls 10 b are provided at both ends ofthe first-insulating-member main portion 10 a in a long-side directionof the sealing plate 2. A pair of second side walls 10 c are provided atboth ends of the first-insulating-member main portion 10 a in ashort-side direction of the sealing plate 2. The secondterminal-receiving hole 10 d is formed in the first-insulating-membermain portion 10 a. First connecting portions 10 e are provided on theouter surfaces of the second side walls 10 c. The first connectingportions 10 e are preferably provided at the centers of the second sidewalls 10 c in the long-side direction of the sealing plate 2. Secondconnecting portions 10 f are also provided on the outer surfaces of thesecond side walls 10 c. The second connecting portions 10 f arepreferably provided at ends of the second side walls 10 c in thelong-side direction of the sealing plate 2. A first groove 10 x isformed in a surface of the first-insulating-member main portion 10 athat faces the sealing plate 2. A second groove 10 y is formed in asurface of the first-insulating-member main portion 10 a that faces theconductive member 61. The second groove 10 y is disposed outside thefirst groove 10 x. The surface of the first-insulating-member mainportion 10 a that faces the sealing plate 2 has recesses 10 g at fourcorners thereof.

As illustrated in FIGS. 6 and 8, the conductive member 61 includes aconductive-member base portion 61 a arranged to face thefirst-insulating-member main portion 10 a and a tubular portion 61 bthat extends toward the electrode assembly 3 from an edge portion of theconductive-member base portion 61 a. The cross sectional shape of thetubular portion 61 b along a plane parallel to the sealing plate 2 maybe either circular or polygonal. The tubular portion 61 b has a flange61 d at an end thereof adjacent to the electrode assembly 3. Aconductive-member opening portion 61 f is provided at the end of thetubular portion 61 b that is adjacent to the electrode assembly 3. Apressing projection 61 e is provided on a surface of theconductive-member base portion 61 a that faces the first insulatingmember 10. The pressing projection 61 e presses the first insulatingmember 10 against the sealing plate 2. The pressing projection 61 e ispreferably provided at or near an edge portion around the thirdterminal-receiving hole 61 c.

Next, the deformation plate 62 is placed to cover the conductive-memberopening portion 61 f of the conductive member 61, and is welded to theconductive member 61 at the peripheral edge thereof by, for example,laser welding. Thus, the conductive-member opening portion 61 f of theconductive member 61 is sealed by the deformation plate 62. Theconductive member 61 and the deformation plate 62 are each preferablymade of a metal, more preferably aluminum or an aluminum alloy.

FIG. 9 is a perspective view of the deformation plate 62. In FIG. 9, theelectrode assembly 3 is at the upper side and the sealing plate 2 is atthe lower side. As illustrated in FIG. 9, the deformation plate 62includes a stepped projection 62 a that projects toward the electrodeassembly 3 at the center thereof. The stepped projection 62 a includes afirst projecting portion 62 a 1 and a second projecting portion 62 a 2that has an outer diameter less than that of the first projectingportion 62 a 1 and that projects toward the electrode assembly 3 fromthe first projecting portion 62 a 1. The deformation plate 62 has anannular rib 62 b that projects toward the electrode assembly 3 at theperipheral edge thereof. An annular thin portion 62 c having an annularshape is provided on a surface of the deformation plate 62 that facesthe electrode assembly 3. The deformation plate 62 may have any shape aslong as the deformation plate 62 is capable of sealing theconductive-member opening portion 61 f of the conductive member 61.

A method for fixing the second insulating member 63 and the firstpositive-electrode current collector 6 a will now be described withreference to FIG. 10. In FIG. 10, surfaces that face the electrodeassembly 3 in the rectangular secondary battery 20 are at the upperside, and surfaces that face the sealing plate 2 are at the lower side.

As illustrated in FIG. 10A, the first positive-electrode currentcollector 6 a has a connection hole 6 c. An edge portion around theconnection hole 6 c is connected to the deformation plate 62 by welding.The first positive-electrode current collector 6 a also has four fixingholes 6 d around the connection hole 6 c. Although the number of fixingholes 6 d may instead be one, two or more fixing holes 6 d arepreferably provided. The first positive-electrode current collector 6 aalso has displacement prevention holes 6 e around the connection hole 6c. Although the number of displacement prevention holes 6 e may be one,at least two displacement prevention holes 6 e are preferably provided.The displacement prevention holes 6 e are preferably disposed betweenthe fixing holes 6 d. Each fixing hole 6 d preferably includes a smalldiameter portion 6 d 1 and a large diameter portion 6 d 2 having aninner diameter greater than that of the small diameter portion 6 dl. Thelarge diameter portion 6 d 2 is preferably closer to the electrodeassembly 3 than the small diameter portion 661 is.

As illustrated in FIGS. 8 and 10A, the second insulating member 63includes an insulating-member first region 63 x arranged to face thedeformation plate 62, an insulating-member second region 63 y arrangedto face the sealing plate 2, and an insulating-member third region 63 zthat connects the insulating-member first region 63 x and theinsulating-member second region 63 y to each other. Theinsulating-member first region 63 x has an insulating-member firstopening 63 a at the center thereof. A third wall portion 63 b isprovided at an end of the insulating-member first region 63 x in thelong-side direction of the sealing plate 2. A third connecting portion63 d is provided on the third wall portion 63 b. Fourth wall portions 63c are provided at both ends of the insulating-member first region 63 xin the short-side direction of the sealing plate 2. Fourth connectingportions 63 e are provided on the fourth wall portions 63 c. Inaddition, four fixing projections 63 f are provided on a surface of theinsulating-member first region 63 x that faces the electrode assembly 3.In addition, two displacement prevention projections 63 g are alsoprovided. Four lug portions 63 h are provided on a surface of theinsulating-member first region 63 x that faces the sealing plate 2. Theinsulating-member second region 63 y is located closer to the sealingplate 2 than the insulating-member first region 63 x is. Theinsulating-member second region 63 y has an insulating-member secondopening 63 i that is located to face the electrolyte introduction hole15 in the sealing plate 2. An insulating-member annular rib 63 k thatextends toward the electrode assembly 3 is provided at an edge portionaround the insulating-member second opening 63 i.

As illustrated in FIG. 10B, the first positive-electrode currentcollector 6 a is placed on the second insulating member 63 such that thefixing projections 63 f of the second insulating member 63 are insertedin the fixing holes 6 d in the first positive-electrode currentcollector 6 a and that the displacement prevention projections 63 g ofthe second insulating member 63 are inserted in the displacementprevention holes 6 e in the first positive-electrode current collector 6a. Then, end portions of the fixing projections 63 f of the secondinsulating member 63 are deformed by, for example, heat crimping. Thus,as illustrated in FIGS. 8C and 10C, large-diameter portions 63 f 1 areformed at the ends of the fixing projections 63 f of the secondinsulating member 63, and the second insulating member 63 and the firstpositive-electrode current collector 6 a are fixed together.

As illustrated in FIG. 8C, the large-diameter portions 63 f 1 formed atthe ends of the fixing projections 63 f of the second insulating member63 are preferably disposed in the large diameter portions 6 d 2 of thefixing holes 6 d.

Unlike the fixing projections 63 f, the displacement preventionprojections 63 g of the second insulating member 63 are not subjected toheat crimping.

The outer diameter of the fixing projections 63 f is preferably greaterthan the outer diameter of the displacement prevention projections 63 g.The inner diameter of the small diameter portions 6 d 1 of the fixingholes 6 d in the first positive-electrode current collector 6 a ispreferably greater than the inner diameter of the displacementprevention holes 6 e in the first positive-electrode current collector 6a.

Next, as illustrated in FIGS. 8A to 8C, the second insulating member 63to which the first positive-electrode current collector 6 a is fixed isconnected to the first insulating member 10 and the conductive member61.

As illustrated in FIG. 8B, the fourth connecting portions 63 e of thesecond insulating member 63 are connected to the first connectingportions 10 e of the first insulating member 10. In addition, asillustrated in FIG. 8C, the lug portions 63 h of the second insulatingmember 63 are connected to the flange 61 d of the conductive member 61.Thus, the second insulating member 63 is connected to the firstinsulating member 10 and the conductive member 61. The second insulatingmember 63 is not necessarily connected to both the first insulatingmember 10 and the conductive member 61. The second insulating member 63is preferably connected to at least one of the first insulating member10 and the conductive member 61. Thus, even when the rectangularsecondary battery 20 is strongly impacted or vibrated, load applied toweak portions of the first positive-electrode current collector 6 a canbe reduced. Accordingly, the risk of damage or breakage of the weakportions of the first positive-electrode current collector 6 a can bereduced.

The deformation plate 62 is connected to the first positive-electrodecurrent collector 6 a by welding. FIG. 11 is an enlarged view of a partof FIG. 8A including the connecting portion between the deformationplate 62 and the first positive-electrode current collector 6 a. Asillustrated in FIG. 11, the second projecting portion 62 a 2 of thedeformation plate 62 is placed in the connection hole 6 c in the firstpositive-electrode current collector 6 a. Then, the second projectingportion 62 a 2 of the deformation plate 62 and the edge portion aroundthe connection hole 6 c in the first positive-electrode currentcollector 6 a are welded and connected together by, for example, laserwelding. The connecting portion between the deformation plate 62 and thefirst positive-electrode current collector 6 a is formed at a positioncorresponding to the position of the insulating-member first opening 63a in the second insulating member 63.

The first positive-electrode current collector 6 a has a thin portion 6f in a region around the connection hole 6 c. The thin portion 6 f hasan annular notch 6 g that surrounds the connection hole 6 c. An annularconnection rib 6 h is formed along the edge portion around theconnection hole 6 c. The connection rib 6 h is connected to thedeformation plate 62 by welding. The first positive-electrode currentcollector 6 a and the deformation plate 62 may be welded either in anannular region over the entire circumference around the connection hole6 c or in a non-annular region having unwelded portions. The firstpositive-electrode current collector 6 a and the deformation plate 62may be welded at multiple locations that are separated from each otheralong the edge portion around the connection hole 6 c.

The operation of the current interruption mechanism 60 will now bedescribed. When the pressure in the battery case 100 increases, thedeformation plate 62 is deformed such that a central portion thereofmoves toward the sealing plate 2. When the pressure in the battery case100 reaches or exceeds a predetermined value, the notch 6 g in the thinportion 6 f of the first positive-electrode current collector 6 a breaksdue to the deformation of the deformation plate 62. Accordingly, theconductive path from the positive electrode plates 4 to the positiveelectrode terminal 7 is broken. Thus, the current interruption mechanism60 includes the first positive-electrode current collector 6 a, thedeformation plate 62, and the conductive member 61. When the rectangularsecondary battery 20 is overcharged and the pressure in the battery case100 is increased, the current interruption mechanism 60 is activated andbreaks the conductive path from the positive electrode plates 4 to thepositive electrode terminal 7. As a result, further overcharging isprevented. The activation pressure at which the current interruptionmechanism 60 is activated may be determined as appropriate.

A leakage test for a welding portion between the conductive member 61and the deformation plate 62 may be performed before welding thedeformation plate 62 and the first positive-electrode current collector6 a together by introducing gas into the space inside the conductivemember 61 through a terminal through hole 7 c formed in the positiveelectrode terminal 7. The terminal through hole 7 c is sealed by aterminal sealing member 7 x. The terminal sealing member 7 x preferablyincludes a metal member 7 y and a rubber member 7 z.

FIG. 12 is a perspective view of the sealing plate 2 to which the firstinsulating member 10, the conductive member 61, the deformation plate62, the second insulating member 63, and the first positive-electrodecurrent collector 6 a are attached. As illustrated in FIG. 12, the thirdconnecting portion 63 d is provided at an end of the second insulatingmember 63 in the long-side direction of the sealing plate 2. Inaddition, the second connecting portions 10 f are provided at both endsof the first insulating member 10 in the short-side direction of theshort-side direction.

[Attachment of Components to Sealing Plate (Negative Electrode Side)]

A method for attaching the negative electrode terminal 9 and the firstnegative-electrode current collector 8 a to the sealing plate 2 will nowbe described with reference to FIGS. 2 and 13. The outer insulatingmember 13 is placed on a surface of the sealing plate 2 that faces theoutside of the battery in a region including anegative-electrode-terminal attachment hole 2 b. An inner insulatingmember 12 and the first negative-electrode current collector 8 a areplaced on a surface of the sealing plate 2 that faces the inside of thebattery in the region including the negative-electrode-terminalattachment hole 2 b. Next, the negative electrode terminal 9 is insertedthrough a through hole in the outer insulating member 13, thenegative-electrode-terminal attachment hole 2 b in the sealing plate 2,a through hole in the inner insulating member 12, and a through hole inthe first negative-electrode current collector 8 a. Then, an end portionof the negative electrode terminal 9 is crimped onto the firstnegative-electrode current collector 8 a. Thus, the outer insulatingmember 13, the sealing plate 2, the inner insulating member 12, and thefirst negative-electrode current collector 8 a are fixed together. Thecrimped portion of the negative electrode terminal 9 is preferablywelded and connected to the first negative-electrode current collector 8a by, for example, laser welding. The inner insulating member 12 and theouter insulating member 13 are each preferably made of a resin.

[Connection Between Current Collectors and Tabs]

FIG. 14 illustrates a method for connecting the positive-electrode tabs40 to the second positive-electrode current collector 6 b and thenegative-electrode tabs 50 to the second negative-electrode currentcollector 8 b. Two electrode assembly elements are produced by theabove-described method, and are referred to as a first electrodeassembly element 3 a and a second electrode assembly element 3 b. Thefirst electrode assembly element 3 a and the second electrode assemblyelement 3 b may have completely the same structure or differentstructures. The positive-electrode tabs 40 of the first electrodeassembly element 3 a form a first positive-electrode tab group 40 a. Thenegative-electrode tabs 50 of the first electrode assembly element 3 aform a first negative-electrode tab group 50 a. The positive-electrodetabs 40 of the second electrode assembly element 3 b form a secondpositive-electrode tab group 40 b. The negative-electrode tabs 50 of thesecond electrode assembly element 3 b form a second negative-electrodetab group 50 b.

The second positive-electrode current collector 6 b and the secondnegative-electrode current collector 8 b are disposed between the firstelectrode assembly element 3 a and the second electrode assembly element3 b. The first positive-electrode tab group 40 a, which is formed of thepositive-electrode tabs 40 in a stacked state that project from thefirst electrode assembly element 3 a, is placed on the secondpositive-electrode current collector 6 b, and the firstnegative-electrode tab group 50 a, which is formed of thenegative-electrode tabs 50 in a stacked state that project from thefirst electrode assembly element 3 a, is placed on the secondnegative-electrode current collector 8 b. The second positive-electrodetab group 40 b, which is formed of the positive-electrode tabs 40 in astacked state that project from the second electrode assembly element 3b, is placed on the second positive-electrode current collector 6 b, andthe second negative-electrode tab group 50 b, which is formed of thenegative-electrode tabs 50 in a stacked state that project from thesecond electrode assembly element 3 b, is placed on the secondnegative-electrode current collector 8 b. The first positive-electrodetab group 40 a and the second positive-electrode tab group 40 b areconnected to the second positive-electrode current collector 6 b bywelding to form welded connecting portions 90. The firstnegative-electrode tab group 50 a and the second negative-electrode tabgroup 50 b are connected to the second negative-electrode currentcollector 8 b by welding to form welded connecting portions 90. Thewelding and connecting process may be performed as described below.

The tabs in a stacked state (the first positive-electrode tab group 40a, the second positive-electrode tab group 40 b, the firstnegative-electrode tab group 50 a, and the second negative-electrode tabgroup 50 b) and the current collectors (the second positive-electrodecurrent collector 6 b and the second negative-electrode currentcollector 8 b) are clamped by a pair of welding jigs from above andbelow and are welded together. The welding method is preferablyultrasonic welding or resistance welding. The pair of welding jigs are apair of resistance welding electrodes for resistance welding, and are ahorn and an anvil for ultrasonic welding. The tabs (the firstpositive-electrode tab group 40 a, the second positive-electrode tabgroup 40 b, the first negative-electrode tab group 50 a, and the secondnegative-electrode tab group 50 b) and the current collectors (thesecond positive-electrode current collector 6 b and the secondnegative-electrode current collector 8 b) may instead be connected bylaser welding.

As illustrated in FIG. 14, the second positive-electrode currentcollector 6 b includes a current-collector first region 6 b 1 and acurrent-collector second region 6 b 2. The positive-electrode tabs 40are connected to the current-collector first region 6 b 1. Acurrent-collector second opening 6 z is formed in the current-collectorfirst region 6 b 1. The current-collector first region 6 b 1 and thecurrent-collector second region 6 b 2 are connected to each other by acurrent-collector third region 6 b 3. When the second positive-electrodecurrent collector 6 b is connected to the first positive-electrodecurrent collector 6 a, the current-collector second opening 6 z is at aposition corresponding to the position of the electrolyte introductionhole 15 in the sealing plate 2. A current-collector first opening 6 y isformed in the current-collector second region 6 b 2. A current-collectorfirst recess 6 m is formed around the current-collector first opening 6y. Target holes 6 k are formed on both sides of the current-collectorfirst opening 6 y in the short-side direction of the sealing plate 2.

As illustrated in FIG. 14, the second negative-electrode currentcollector 8 b includes a current-collector first region 8 b 1 and acurrent-collector second region 8 b 2. The negative-electrode tabs 50are connected to the current-collector first region 8 b 1. Acurrent-collector first opening 8 y is formed in the current-collectorsecond region 8 b 2. A current-collector first recess 8 f is formedaround the current-collector first opening 8 y. Target holes 8 e areformed on both sides of the current-collector first opening 8 y in theshort-side direction of the sealing plate 2.

[Connection Between First Positive-Electrode Current Collector andSecond Positive-Electrode Current Collector]

As illustrated in FIGS. 2, 7, and 8 and other drawings, the secondpositive-electrode current collector 6 b is placed on the secondinsulating member 63 such that a current-collector projection 6 x on thefirst positive-electrode current collector 6 a is inserted in thecurrent-collector first opening 6 y in the second positive-electrodecurrent collector 6 b. Then, the current-collector projection 6 x on thefirst positive-electrode current collector 6 a is welded to an edgeportion around the current-collector first opening 6 y in the secondpositive-electrode current collector 6 b by irradiation with an energyray, such as a laser beam. Thus, the first positive-electrode currentcollector 6 a and the second positive-electrode current collector 6 bare connected together. The first positive-electrode current collector 6a and the second positive-electrode current collector 6 b are preferablywelded together in the current-collector first recess 6 m.

As illustrated in FIGS. 2 and 8, the distance between the sealing plate2 and the current-collector first region 6 b 1 is less than the distancebetween the sealing plate 2 and the current-collector second region 6 b2 in the direction perpendicular to the sealing plate 2. According tothis structure, the space occupied by the current collecting unit can bereduced, and the volume energy density of the rectangular secondarybattery can be increased.

When the first positive-electrode current collector 6 a and the secondpositive-electrode current collector 6 b are welded together byirradiation with an energy ray, such as a laser beam, the target holes 6k are preferably used as image correction targets.

As illustrated in FIG. 8A, the first positive-electrode currentcollector 6 a has a current-collector second recess 6 w in a surfacethereof that faces the second insulating member 63 at a position behindthe current-collector projection 6 x. Accordingly, a larger weldedconnecting portion can be more easily formed between the firstpositive-electrode current collector 6 a and the secondpositive-electrode current collector 6 b. In addition, thecurrent-collector second recess 6 w reduces the risk that the secondinsulating member 63 will be damaged by heat generated in the weldingprocess when the first positive-electrode current collector 6 a and thesecond positive-electrode current collector 6 b are connected togetherby welding.

[Connection Between First Negative-Electrode Current Collector andSecond Negative-Electrode Current Collector]

As illustrated in FIG. 13, the second negative-electrode currentcollector 8 b includes the current-collector first region 8 b 1 and thecurrent-collector second region 8 b 2. The negative-electrode tabs 50are connected to the current-collector first region 8 b 1. Thecurrent-collector first opening 8 y is formed in the current-collectorsecond region 8 b 2. The current-collector first region 8 b 1 and thecurrent-collector second region 8 b 2 are connected to each other by acurrent-collector third region 8 b 3.

As illustrated in FIG. 13, the second negative-electrode currentcollector 8 b is placed on the inner insulating member 12 such that acurrent-collector projection 8 x on the first negative-electrode currentcollector 8 a is inserted in the current-collector first opening 8 y inthe second negative-electrode current collector 8 b. Then, thecurrent-collector projection 8 x on the first negative-electrode currentcollector 8 a is welded to an edge portion around the current-collectorfirst opening 8 y in the second negative-electrode current collector 8 bby irradiation with an energy ray, such as a laser beam. Thus, the firstnegative-electrode current collector 8 a and the secondnegative-electrode current collector 8 b are connected together. Thefirst negative-electrode current collector 8 a and the secondnegative-electrode current collector 8 b are preferably welded togetherin the current-collector first recess 8 f. Similar to the secondpositive-electrode current collector 6 b, the second negative-electrodecurrent collector 8 b has the target holes 8 e. The distance between thesealing plate 2 and the current-collector first region 8 b 1 is lessthan the distance between the sealing plate 2 and the current-collectorsecond region 8 b 2 in the direction perpendicular to the sealing plate2. The first negative-electrode current collector 8 a may be omitted,and the second negative-electrode current collector 8 b may be connectedto the negative electrode terminal 9.

As illustrated in FIG. 13, the first negative-electrode currentcollector 8 a has a current-collector second recess 8 w in a surfacethereof that faces the inner insulating member 12 at a position behindthe current-collector projection 8 x. Accordingly, a larger weldedconnecting portion can be more easily formed between the firstnegative-electrode current collector 8 a and the secondnegative-electrode current collector 8 b. In addition, thecurrent-collector second recess 8 w reduces the risk that the innerinsulating member 12 will be damaged by heat generated in the weldingprocess when the first negative-electrode current collector 8 a and thesecond negative-electrode current collector 8 b are connected togetherby welding.

The current-collector projection 6 x and the current-collectorprojection 8 x are preferably not circular, and are preferablyrectangular, elliptical, or track-shaped in plan view.

[Attachment of Cover]

FIG. 15 is a perspective view of the sealing plate 2 to which thecomponents are attached and a cover 80. The positive-electrode tabs 40are not illustrated in FIG. 15. The cover 80 includes a cover mainportion 80 a arranged to face the first positive-electrode currentcollector 6 a and a pair of arm portions 80 b that extend toward thesealing plate 2 from both ends of the cover main portion 80 a in theshort-side direction of the sealing plate 2. The cover 80 also includesa cover wall portion 80 e that extends toward the sealing plate 2 froman end of the cover main portion 80 a in the long-side direction of thesealing plate 2. Connecting projections 80 c are provided on innersurfaces of the arm portions 80 b. The cover main portion 80 a has baseopenings 80 d at positions near the base ends of the arm portions 80 b.The cover wall portion 80 e has a wall portion opening 80 f.

As illustrated in FIGS. 16A and 16B, the cover 80 is connected to thefirst insulating member 10 and the second insulating member 63 so thatthe cover main portion 80 a of the cover 80 faces the firstpositive-electrode current collector 6 a. The connecting projections 80c on the pair of arm portions 80 b of the cover 80 are connected to thesecond connecting portions 10 f of the first insulating member 10. Thecover wall portion 80 e of the cover 80 is connected to the thirdconnecting portion 63 d of the second insulating member 63.

As illustrated in FIG. 17A, the third connecting portion 63 d is aprojection provided on the third wall portion 63 b. The third connectingportion 63 d is fitted to the wall portion opening 80 f in the coverwall portion 80 e so that the first insulating member 10 and the cover80 are connected together. As illustrated in FIG. 17B, the connectingprojections 80 c on the arm portions 80 b of the cover 80 are connectedto the second connecting portions 10 f of the first insulating member 10by being engaged therewith.

The cover 80 is preferably made of resin. In addition, the cover 80 ispreferably composed of an insulating member.

As illustrated in FIGS. 17A and 17B, a gap is preferably providedbetween the first positive-electrode current collector 6 a and the topsurface of the cover main portion 80 a of the cover 80. Such a structureallows gas to smoothly flow along the bottom surface of the deformationplate 62, so that the deformation plate 62 is smoothly deformed when thepressure in the battery case 100 reaches or exceeds the predeterminedvalue. However, it is not necessary that the above-described gap beprovided.

As illustrated in FIG. 17B, the cover main portion 80 a of the cover 80preferably has the base openings 80 d. In such a case, gas smoothlyflows along the bottom surface of the deformation plate 62, so that thedeformation plate 62 is smoothly deformed when the pressure in thebattery case 100 reaches or exceeds the predetermined value. However, itis not necessary that the base openings 80 d be provided.

[Production of Electrode Assembly]

The first positive-electrode tab group 40 a, the secondpositive-electrode tab group 40 b, the first negative-electrode tabgroup 50 a, and the second negative-electrode tab group 50 b are bent sothat the top surfaces of the first electrode assembly element 3 a andthe second electrode assembly element 3 b illustrated in FIG. 14 are incontact with each other directly or with another component interposedtherebetween. Thus, the first electrode assembly element 3 a and thesecond electrode assembly element 3 b are combined together to form asingle electrode assembly 3. The first electrode assembly element 3 aand the second electrode assembly element 3 b are preferably combinedtogether by using a piece of tape or the like. Alternatively, the firstelectrode assembly element 3 a and the second electrode assembly element3 b are preferably combined together by placing the first electrodeassembly element 3 a and the second electrode assembly element 3 b inthe insulating sheet 14 formed in a box shape or a bag shape.

[Assembly of Rectangular Secondary Battery]

The electrode assembly 3 attached to the sealing plate 2 is covered withthe insulating sheet 14, and is inserted into the rectangular exteriorbody 1. The insulating sheet 14 is preferably flat sheet shaped, and isfolded into a box shape or a bag shape. Then, the sealing plate 2 andthe rectangular exterior body 1 are joined together by, for example,laser welding to seal the opening in the rectangular exterior body 1.After that, a nonaqueous electrolyte containing an electrolyte solventand an electrolyte salt is introduced into the battery case 100 throughthe electrolyte introduction hole 15 in the sealing plate 2. Then, theelectrolyte introduction hole 15 is sealed with the sealing plug 16.Thus, the rectangular secondary battery 20 is produced.

[Regarding Rectangular Secondary Battery 20]

As illustrated in FIGS. 8, 17, and 18, the conductive member 61 includesa pressing projection 61 e that projects toward the first insulatingmember 10 in a region where the conductive member 61 faces the firstinsulating member 10. Accordingly, the pressing projection 61 e stronglypresses the first insulating member 10 against the sealing plate 2.Therefore, gas around the electrode assembly 3 does not flow through agap between the sealing plate 2 and the first insulating member 10 or agap between the first insulating member 10 and the conductive member 61toward the connecting portion between the conductive member 61 and thepositive electrode terminal 7. As a result, gas does not flow into thespace defined by the conductive member 61 and the deformation plate 62through a gap between the conductive member 61 and the positiveelectrode terminal 7. This ensures reliable activation of the currentinterruption mechanism 60 when the pressure in the rectangular exteriorbody 1 increases in case of abnormal operation of the rectangularsecondary battery 20. Thus, the reliability of the rectangular secondarybattery 20 is increased.

The pressing projection 61 e is formed on a surface of theconductive-member base portion 61 a of the conductive member 61 thatfaces the sealing plate 2. When the conductive member 61 and thepositive electrode terminal 7 are viewed in the direction perpendicularto the sealing plate 2, the pressing projection 61 e preferably overlapsa crimped portion 7 d (large diameter portion) of the inserting portion7 b of the positive electrode terminal 7. In addition, the pressingprojection 61 e is preferably formed along the edge of the thirdterminal-receiving hole 61 c in the conductive member 61. However, thepressing projection 61 e may instead be formed at a position separatedfrom the edge of the third terminal-receiving hole 61 c in theconductive member 61. The pressing projection 61 e preferably has anannular shape in plan view. However, the shape of the pressingprojection 61 e in plan view is not limited to an annular shape, and mayinstead be a shape obtained by partially cutting an annular shape. Forexample, the length of the pressing projection 61 e may be 70% or moreof that in the case where the pressing projection 61 e has an annularshape. When the pressing projection 61 e is formed on the conductivemember 61, the pressing projection 61 e can be easily formed in adesired shape.

When the first insulating member 10 pressed by the pressing projection61 e is deformed to move in the horizontal direction (direction parallelto the sealing plate 2, leftward in FIG. 18), there is a risk that a gapwill be formed between the sealing plate 2 and the first insulatingmember 10 or between the first insulating member 10 and the conductivemember 61 due to the deformation of the first insulating member 10. Sucha risk can be reduced by forming a groove in a portion of the firstinsulating member 10 that is disposed between the sealing plate 2 andthe conductive member 61 and that is on the outer side of the pressingprojection 61 e in the radial direction of the second terminal-receivinghole 10 d in the first insulating member 10. For example, a first groove10 x is preferably formed in a surface of the first insulating member 10that faces the sealing plate 2. Also, a second groove 10 y is preferablyformed in a surface of the first insulating member 10 that faces theconductive member 61 in addition to or in place of the first groove 10x. The first insulating member 10 may have only one of the first groove10 x and the second groove 10 y. Alternatively, the first insulatingmember 10 may have the second groove 10 y in the surface thereof facingthe sealing plate 2, and the first groove 10 x in the surface thereoffacing the conductive member 61. The first groove 10 x and the secondgroove 10 y are not essential.

The first groove 10 x preferably has an annular shape in plan view. Thesecond groove 10 y preferably also has an annular shape in plan view.However, the shape of the first groove 10 x and the second groove 10 yin plan view is not limited to an annular shape, and may instead be ashape obtained by partially cutting an annular shape. For example, thelength of the first groove 10 x and the second groove 10 y may be 70% ormore of that in the case where the first groove 10 x and the secondgroove 10 y have an annular shape.

When grooves are formed in both surfaces of the first insulating member10, the grooves are preferably arranged such that one of the grooves ison the outer side the other groove in the radial direction of the secondterminal-receiving hole 10 d in the first insulating member 10. In otherwords, when the grooves are formed in both surfaces of the firstinsulating member 10, the distance from the second terminal-receivinghole 10 d in the first insulating member 10 to one of the grooves ispreferably greater than the distance from the second terminal-receivinghole 10 d in the first insulating member 10 to the other groove.

In addition, the distance between the center of one of the grooves andthe center of the other groove in the radial direction of the secondterminal-receiving hole 10 d in the first insulating member 10 (distanceD in FIG. 18) is preferably 0.5 mm to 10 mm, and more preferably 0.5 mmto 5 mm.

For example, the first insulating member 10 is formed such that thesecond groove 10 y is on the outer side of the first groove 10 x in theradial direction of the second terminal-receiving hole 10 d in the firstinsulating member 10. Referring to FIG. 18, the distance D between thecenter of the first groove 10 x in the width direction and the center ofthe second groove 10 y in the width direction is preferably 0.5 mm to 10mm, and more preferably 0.5 mm to 5 mm. The width of the first groove 10x and the second groove 10 y (width in the left-right direction in FIG.18) is preferably 0.5 mm to 2 mm.

Preferably, the first groove 10 x and the second groove 10 y partiallyoverlap in plan view of the first insulating member 10. However,preferably, the first groove 10 x and the second groove 10 y do notcompletely overlap in plan view of the first insulating member 10.According to such a structure, deformation of the first insulatingmember 10 can be more effectively reduced.

The width of the pressing projection 61 e in the radial direction of thethird terminal-receiving hole 61 c in the conductive member 61 ispreferably 5 mm or less, and more preferably 2 mm. The distance betweenthe pressing projection 61 e and the first groove 10 x in the radialdirection of the third terminal-receiving hole 61 c in the conductivemember 61 is preferably 0.5 mm to 5 mm, more preferably 0.5 mm to 2 mm,and still more preferably 0.5 mm to 1 mm.

The above configuration is particularly effective when the firstinsulating member 10 is made of a relatively soft material, such asperfluoroalkoxy alkane (PFA) or polytetrafluoroethylene (PTFE).

As illustrated in FIG. 18, an edge portion around the thirdterminal-receiving hole 61 c in the conductive member 61 preferablyincludes a tapered portion 61 g on a side thereof facing the electrodeassembly 3. According to such a structure, a gap is not easily formedbetween the positive electrode terminal 7 and the conductive member 61,and the risk that gas will flow through the gap between the positiveelectrode terminal 7 and the conductive member 61 can be effectivelyreduced.

The conductive member 61 is preferably made of aluminum or an aluminumalloy. The positive electrode terminal 7 is also preferably made ofaluminum or an aluminum alloy.

As illustrated in FIG. 10, the second insulating member 63 and the firstpositive-electrode current collector 6 a are fixed together by insertingthe fixing projections 63 f of the second insulating member 63 into thefixing holes 6 d in the first positive-electrode current collector 6 aand forming the large-diameter portions 63 f 1 by increasing thediameter of the end portions of the fixing projections 63 f. Accordingto this structure, load applied to weak portions of the firstpositive-electrode current collector 6 a, such as the thin portion 6 fand the notch 6 g, can be reduced when the rectangular secondary battery20 is strongly impacted or vibrated. The second insulating member 63 ispreferably connected to at least one of the first insulating member 10and the conductive member 61.

In the case where the second insulating member 63 is made of resin,there is a risk that gaps will be formed between side surfaces of thefixing projections 63 f of the second insulating member 63 and the innersurfaces of the fixing holes 6 d in the first positive-electrode currentcollector 6 a due to distortion or contraction of the fixing projections63 f when the diameter of the end portions of the fixing projections 63f is increased after inserting the fixing projections 63 f into thefixing holes 6 d. Such gaps may cause a displacement of the firstpositive-electrode current collector 6 a with respect to the secondinsulating member 63 in a direction parallel to the sealing plate 2 whenthe rectangular secondary battery 20 is strongly impacted or vibrated.In the case where the end portions of the fixing projections 63 f areincreased in diameter while being heated, the above-described gaps areeasily formed due to thermal contraction of portions of the fixingprojections 63 f in the fixing holes 6 d.

The rectangular secondary battery 20 is configured such that the secondinsulating member 63 includes the displacement prevention projections 63g and that the displacement prevention projections 63 g are disposed inthe displacement prevention holes 6 e in the first positive-electrodecurrent collector 6 a. Unlike the fixing projections 63 f, thedisplacement prevention projections 63 g are not increased in diameter.Therefore, even when gaps are formed between the fixing projections 63 fand the fixing holes 6 d, since the displacement prevention projections63 g are fitted to the displacement prevention holes 6 e, displacementof the first positive-electrode current collector 6 a with respect tothe second insulating member 63 can be effectively reduced.

Preferably, a plurality of fixing projections 63 f are provided aroundthe connecting portion between the deformation plate 62 and the firstpositive-electrode current collector 6 a. In particular, the fixingprojections 63 f are preferably provided at four or more locations. Thedisplacement prevention projections 63 g are preferably provided on bothsides of the connecting portion between the deformation plate 62 and thefirst positive-electrode current collector 6 a. In addition, thedisplacement prevention projections 63 g are preferably disposed betweenthe fixing projections 63 f.

The diameter of the fixing projections 63 f is preferably greater thanthe diameter of the displacement prevention projections 63 g.

When the displacement prevention holes 6 e are provided at twolocations, the inner diameter of one displacement prevention hole 6 emay be greater than that of the other. In addition, when thedisplacement prevention projections 63 g are provided at two locations,the outer diameter of one displacement prevention projection 63 g may begreater than that of the other.

The ratio of the outer diameter of the displacement preventionprojections 63 g to the inner diameter of the displacement preventionholes 6 e is preferably 0.95 to 1. The difference between the innerdiameter of the displacement prevention holes 6 e and the outer diameterof the displacement prevention projections 63 g is preferably less thanor equal to 0.1 mm.

When a plurality of fitting portions at which the displacementprevention projections 63 g are fitted to the displacement preventionholes 6 e are provided, the difference between the inner diameter of thedisplacement prevention hole 6 e and the outer diameter of thedisplacement prevention projection 63 g at one of the fitting portionsmay differ from the difference between the inner diameter of thedisplacement prevention hole 6 e and the outer diameter of thedisplacement prevention projection 63 g at another one of the fittingportions.

Preferably, each displacement prevention hole 6 e is not a notch formedin an edge portion of the first positive-electrode current collector 6a, but is formed such that an edge portion therearound has an annularshape. In other words, the side surface of each displacement preventionprojection 63 g is preferably surrounded by the first positive-electrodecurrent collector 6 a over the entire circumference thereof. In such acase, displacement can be more effectively reduced.

Preferably, the displacement prevention holes 6 e are provided on bothsides of the connecting portion between the deformation plate 62 and thefirst positive-electrode current collector 6 a in the short-sidedirection of the sealing plate 2. In addition, preferably, theconnecting portion between the deformation plate 62 and the firstpositive-electrode current collector 6 a is disposed between twodisplacement prevention holes 6 e on a straight line connecting the twodisplacement prevention holes 6 e. Accordingly, load applied to theconnecting portion between the deformation plate 62 and the firstpositive-electrode current collector 6 a, the thin portion 6 f, and thenotch 6 g can be reliably reduced.

The end portions of the fixing projections 63 f preferably have,recesses before the diameter thereof is increased. In such a case, loadapplied to the base ends of the fixing projections 63 f when the endportions of the fixing projections 63 f are increased in diameter can bereduced.

As illustrated in FIGS. 16 and 17, the cover 80 is disposed between thefirst positive-electrode current collector 6 a and the electrodeassembly 3. According to this structure, even when the rectangularsecondary battery 20 is strongly impacted or vibrated and the electrodeassembly 3 is moved toward the sealing plate 2, the electrode assembly 3can be prevented from coming into contact with the firstpositive-electrode current collector 6 a and causing damage or breakageof, for example, the weak portions of the first positive-electrodecurrent collector 6 a, such as the thin portion 6 f and the notch 6 g,and the connecting portion between the deformation plate 62 and thefirst positive-electrode current collector 6 a. Accordingly, a secondarybattery with increased reliability can be provided. The cover 80 ispreferably made of resin. In addition, the cover 80 is preferablyelectrically insulative.

The cover 80 is preferably formed as a component separate from the firstinsulating member 10 and the second insulating member 63. When, forexample, the cover 80 is a component separate from the first insulatingmember 10 and the second insulating member 63, the secondary battery canbe easily assembled. In addition, when the cover 80 and the secondinsulating member 63 are separate components, a projection may be formedon a surface of the second insulating member 63 that faces the firstpositive-electrode current collector 6 a, and the second insulatingmember 63 and the first positive-electrode current collector 6 a can bestrongly connected together by using the projection.

A gap is preferably provided between the first positive-electrodecurrent collector 6 a and the cover main portion 80 a of the cover 80.The distance between a surface of the first positive-electrode currentcollector 6 a that faces the electrode assembly and a surface of thecover main portion 80 a that faces the sealing plate is preferably 0.1mm to 5 mm, and more preferably 0.5 to 2 mm.

Preferably, a portion of the cover 80 that extends toward the sealingplate 2 from the cover main portion 80 a is connected to at least one ofthe first insulating member 10 and the second insulating member 63 sothat a gap is provided between the first positive-electrode currentcollector 6 a and the cover main portion 80 a. According to thisstructure, even when the electrode assembly 3 moves toward the sealingplate 2 and comes into contact with the cover 80, the cover 80 absorbsthe impact to some extent and thereby prevents the electrode assembly 3from being damaged.

Preferably, the cover 80 is connected to at least one of the firstinsulating member 10 and the second insulating member 63. Morepreferably, the cover 80 is connected to each of the first insulatingmember 10 and the second insulating member 63. For example, preferably,the cover 80 includes the cover main portion 80 a and the pair of armportions 80 b that extend from the cover main portion 80 a toward thesealing plate 2, and the arm portions 80 b are connected to the firstinsulating member 10. In addition, preferably, the cover main portion 80a is provided with the cover wall portion 80 e, and the cover wallportion 80 e is connected to the second insulating member 63.

The cover main portion 80 a preferably has through holes. Such astructure enables gas to smoothly flow below the deformation plate 62.The base openings 80 d formed in the cover main portion 80 a atpositions near the base ends of the arm portions 80 b preferably serveas the through holes.

When the positive-electrode current collecting member includes the firstpositive-electrode current collector 6 a and the secondpositive-electrode current collector 6 b, the cover 80 is preferablydisposed between the electrode assembly 3 and the connecting portionbetween the first positive-electrode current collector 6 a and thesecond positive-electrode current collector 6 b. According to thisstructure, even when the rectangular secondary battery 20 is stronglyvibrated or impacted and the electrode assembly 3 is moved toward thesealing plate 2, the electrode assembly 3 can be prevented from cominginto contact with the connecting portion between the firstpositive-electrode current collector 6 a and the secondpositive-electrode current collector 6 b and causing damage or breakageof the connecting portion between the first positive-electrode currentcollector 6 a and the second positive-electrode 6 b current collector. Asurface of the cover main portion 80 a that faces the firstpositive-electrode current collector 6 a is preferably formed such thata portion thereof that faces the connecting portion between the firstpositive-electrode current collector 6 a and the secondpositive-electrode current collector 6 b is recessed from a portionthereof that faces the connecting portion between the deformation plate62 and the first positive-electrode current collector 6 a.

The cover 80 is preferably connected to at least one of the firstinsulating member 10 and the second insulating member 63 after thesecond positive-electrode current collector 6 b to which thepositive-electrode tabs 40 are connected is connected to the firstpositive-electrode current collector 6 a to which the deformation plate62 is connected.

As illustrated in FIGS. 8 and 9, the deformation plate 62 includes theannular rib 62 b that projects toward the electrode assembly 3 (upwardin FIG. 9) at the outer peripheral edge thereof. The annular rib 62 b isfitted to an end portion of the tubular portion 61 b of the conductivemember 61 that is adjacent to the electrode assembly 3, and is connectedto the conductive member 61 by welding. The deformation plate 62 alsoincludes the annular thin portion 62 c in a region closer to the centerthan the annular rib 62 b is. According to this structure, even if thethickness of the deformation plate 62 is increased, the deformationplate 62 can be smoothly deformed when the pressure in the rectangularexterior body 1 reaches or exceeds the predetermined value. The thermalcapacity of the deformation plate 62 can be increased by increasing thethickness of the deformation plate 62. Therefore, even when the weakportions of the first positive-electrode current collector 6 a, such asthe thin portion 6 f and the notch 6 g, are heated, the generated heatis transferred to the deformation plate 62, and fusion breakage of theweak portions of the first positive-electrode current collector 6 a,such as the thin portion 6 f and the notch 6 g, can be prevented. Theannular connection rib 6 h is preferably provided along the edge portionaround the connection hole 6 c in the first positive-electrode currentcollector 6 a. Accordingly, the thermal capacity of the firstpositive-electrode current collector 6 a can be increased in regionsaround the weak portions thereof, such as the thin portion 6 f and thenotch 6 g. As a result, fusion breakage of the weak portions of thefirst positive-electrode current collector 6 a, such as the thin portion6 f and the notch 6 g, can be more effectively prevented.

The deformation plate 62 is preferably inclined toward the sealing plate2 in the direction from the outer peripheral edge toward the centerthereof. The annular thin portion 62 c is preferably formed by forming arecess in a surface of the deformation plate 62 that faces the electrodeassembly 3. Such a configuration enables a smooth deformation of thedeformation plate 62. The width of the annular thin portion 62 c in planview is preferably 1 mm to 3 mm, and more preferably 1.5 mm to 2 mm.

After the gas discharge valve 17 breaks and gas in the battery case 100is discharged to the outside of the battery case 100, the deformationplate 62 remains unbroken and the conductive-member opening portion 61 fin the conductive member 61 is sealed by the deformation plate 62.

As illustrated in FIGS. 9 and 11, the deformation plate 62 includes thestepped projection 62 a including the first projecting portion 62 a 1and the second projecting portion 62 a 2 in a central region thereof.The second projecting portion 62 a 2 is fitted to the connection hole 6c in the first positive-electrode current collector 6 a. The outerdiameter of the first projecting portion 62 a 1 is greater than theinner diameter of the connection hole 6 c, so that a surface of thefirst projecting portion 62 al that faces the electrode assembly 3 is incontact with a top surface 6 i of the first positive-electrode currentcollector 6 a. According to this structure, when the connecting portionbetween the second projecting portion 62 a 2 of the deformation plate 62and the connection hole 6 c in the first positive-electrode currentcollector 6 a is irradiated with an energy ray, such as a laser beam,the energy ray is prevented from passing through a gap between the firstprojecting portion 62 a 1 and a side wall of the connection hole 6 c inthe first positive-electrode current collector 6 a and being scatteredin a region above the first positive-electrode current collector 6 a.Accordingly, damage or breakage of components due to the energy ray canbe reliably prevented. The stepped projection 62 a preferably has astepped recess in a surface thereof that faces the sealing plate 2. Thestepped recess preferably has a bottom portion 62 d that is closer tothe sealing plate 2 than the top surface 6 i of the firstpositive-electrode current collector 6 a is.

First Modification

A rectangular secondary battery according to a first modification has astructure similar to that of the rectangular secondary battery 20according to the embodiment except for the shape of the cover. Asillustrated in FIGS. 19A and 19B, a cover 81 according to the firstmodification includes a cover main portion 81 a arranged to face thefirst positive-electrode current collector 6 a and a pair of armportions 81 b that extend toward the sealing plate 2 from both ends ofthe cover main portion 81 a in the short-side direction of the sealingplate 2. The cover 81 also includes a cover wall portion 81 e thatextends toward the sealing plate 2 from an end of the cover main portion81 a in the long-side direction of the sealing plate 2. Connectingprojections are provided on inner surfaces of the arm portions 81 b. Theconnecting projections are connected to the second connecting portions10 f of the first insulating member 10.

The cover main portion 81 a has base openings 81 d at positions near thebase ends of the arm portions 81 b. The cover wall portion 81 e has awall portion opening 81 f. The cover 81 of the rectangular secondarybattery according to the first modification has a cover opening 81 x inthe cover main portion 81 a. The cover opening 81 x is located such thatthe cover opening 81 x faces the connecting portion between thedeformation plate 62 and the first positive-electrode current collector6 a. Accordingly, the current interruption mechanism can be moresmoothly activated.

Second Modification

The rectangular secondary battery 20 according to the above-describedembodiment is configured such that the conductive member 61 includes thepressing projection 61 e in the region where the conductive member 61faces the first insulating member 10. A rectangular secondary batteryaccording to a second modification has a structure similar to that ofthe rectangular secondary battery 20 according to the above-describedembodiment except that a pressing projection is provided not on theconductive member but on a portion of the sealing plate that faces thefirst insulating member 10.

FIG. 20 is a sectional view of a part of the secondary battery accordingto the second modification, the part including a current interruptionmechanism. The sectional view of FIG. 20 corresponds to FIG. 8B. Asillustrated in FIG. 20, a pressing projection 102 x is provided on aportion of a sealing plate 102 that faces the first insulating member10. According to this structure, the first insulating member 10 isstrongly pressed by the pressing projection 102 x, so that gas does notflow toward the connecting portion between a conductive member 161 andthe positive electrode terminal 7. Accordingly, gas in the region aroundthe electrode assembly does not leak into the space defined by theconductive member 161 and the deformation plate 62. As a result, a delayin the activation of the current interruption mechanism can beprevented. In addition, when the sealing plate 102 includes the pressingprojection 102 x, the first insulating member 10 can be easily preventedfrom being warped such that a peripheral portion thereof approaches theelectrode assembly 3. The pressing projection 102 x preferably has anannular shape in plan view.

When the sealing plate 102 and the positive electrode terminal 7 areviewed in the direction perpendicular to the sealing plate 102, thepressing projection 102 x preferably overlaps the crimped portion 7 d(large diameter portion) of the inserting portion 7 b of the positiveelectrode terminal 7.

The rectangular secondary battery according to the second modificationis configured such that the conductive member 161 has no pressingprojection. However, the conductive member 161 may also have a pressingprojection.

<Others>

Portions expected to break in response to a deformation of thedeformation plate are preferably the weak portions of the currentcollecting member, the connecting portion between the current collectingmember and the deformation plate, or the weak portions of thedeformation plate. Preferred examples of the weak portions include thinportions and notches.

The first insulating member, the second insulating member, and the coverare preferably made of a resin. For example, polypropylene,polyethylene, perfluoroalkoxy alkane (PFA), polytetrafluoroethylene(PTFE), or ethylene tetrafluoroethylene copolymer (ETFE) may be used.

In the above-described embodiment, the electrode assembly 3 is formed oftwo electrode assembly elements (3 a and 3 b). However, the electrodeassembly 3 is not limited to this. The electrode assembly 3 may insteadbe a single stacked electrode assembly. Alternatively, the electrodeassembly 3 may be a single wound electrode assembly in which anelongated positive electrode plate and an elongated negative electrodeplate are wound with a separator interposed therebetween. Also, each ofthe electrode assembly elements (3 a and 3 b) is not limited to astacked electrode assembly, and may instead be a wound electrodeassembly in which an elongated positive electrode plate and an elongatednegative electrode plate are wound with a separator interposedtherebetween.

When the electrode assembly is a stacked electrode assembly including aplurality of positive electrode plates and a plurality of negativeelectrode plates or when the electrode assembly is a wound electrodeassembly having a winding axis extending in a direction perpendicular tothe sealing plate, the electrode assembly is preferably configured suchthat end portions of the positive electrode plates, end portions of thenegative electrode plates, and end portions of the separators areadjacent to the sealing plate. According to this structure, when thesealing plate has the electrolyte introduction hole, the electrolyte canbe easily introduced into the electrode assembly. In this case, the endportions of the separators that are adjacent to the sealing platepreferably project toward the sealing plate 2 beyond the end portions ofthe negative electrode active material mixture layers of the negativeelectrode plates that are adjacent to the sealing plate. In addition,the electrode assembly is preferably configured such that the endportions of the separators that are adjacent to the sealing plateproject toward the sealing plate beyond the end portions of the positiveelectrode active material mixture layers of the positive electrodeplates that are adjacent to the sealing plate. In addition, preferably,the positive electrode plates and the separators are bonded together byadhesive layers, and the negative electrode plates and the separatorsare bonded together by adhesive layers. According to this structure, therisk that the positive electrode active material mixture layers and thenegative electrode active material mixture layers will come into contactwith the second insulating member and the positive electrode activematerial layers or the negative electrode active material layers will bedamaged can be reliably eliminated.

REFERENCE SIGNS LIST

20 . . . rectangular secondary battery 1 . . . rectangular exterior body2 . . . sealing plate 2 a . . . positive-electrode-terminal attachmenthole 2 b . . . negative-electrode-terminal attachment hole 100 . . .battery case 3 . . . electrode assembly 3 a . . . first electrodeassembly element 3 b . . . second electrode assembly element 4 . . .positive electrode plate 4 a . . . positive electrode core 4 b . . .positive electrode active material mixture layer 4 d . . .positive-electrode protecting layer 40 . . . positive-electrode tab 40 a. . . first positive-electrode tab group 40 b . . . secondpositive-electrode tab group 5 . . . negative electrode plate 5 a . . .negative electrode core 5 b . . . negative electrode active materialmixture layer 50 . . . negative-electrode tab 50 a . . . firstnegative-electrode tab group 50 b . . . second negative-electrode tabgroup 6 . . . positive-electrode current collecting member 6 a . . .first positive-electrode current collector 6 c . . . connection hole 6 d. . . fixing hole 6 dl . . . small diameter portion 6 d 2 . . . largediameter portion 6 e . . . displacement prevention hole 6 f . . . thinportion 6 g . . . notch 6 h . . . connection rib 6 i . . . top surface 6x . . . current-collector projection 6 w . . . current-collector secondrecess 6 b . . . second positive-electrode current collector 6 b 1 . . .current-collector first region 6 b 2 . . . current-collector secondregion 6 b 3 . . . current-collector third region 6 k . . . target hole6 m . . . current-collector first recess 6 y . . . current-collectorfirst opening 6 z . . . current-collector second opening 7 . . .positive electrode terminal 7 a . . . flange 7 b . . . inserting portion7 c . . . terminal through hole 7 d . . . crimped portion 7 x . . .terminal sealing member 7 y . . . metal member 7 z . . . rubber member 8. . . negative-electrode current collecting member 8 a . . . firstnegative-electrode current collector 8 x . . . current-collectorprojection 8 w . . . current-collector second recess 8 b . . . secondnegative-electrode current collector 8 b 1 . . . current-collector firstregion 8 b 2 . . . current-collector second region 8 b 3 . . .current-collector third region 8 e . . . target hole 8 f . . .current-collector first recess 8 y . . . current-collector first opening9 . . . negative electrode terminal 10 . . . first insulating member 10a . . . first-insulating-member main portion 10 b . . . first side wall10 c . . . second side wall 10 d . . . second terminal-receiving hole 10e . . . first connecting portion 10 f . . . second connecting portion 10g . . . recess 10 x . . . first groove 10 y . . . second groove 11 . . .outer insulating member 11 a . . . first terminal-receiving hole 12 . .. inner insulating member 13 . . . outer insulating member 14 . . .insulating sheet 15 . . . electrolyte introduction hole 16 . . . sealingplug 17 . . . gas discharge valve 60 . . . current interruptionmechanism 61 . . . conductive member 61 a . . . conductive-member baseportion 61 b . . . tubular portion 61 c . . . third terminal-receivinghole 61 d . . . flange 61 e . . . pressing projection 61 f . . .conductive-member opening portion 61 g . . . tapered portion 62 . . .deformation plate 62 a . . . stepped projection 62 al . . . firstprojecting portion 62 a 2 . . . second projecting portion 62 b . . .annular rib 62 c . . . annular thin portion 62 d . . . bottom portion ofstepped recess 63 . . . second insulating member 63 x . . .insulating-member first region 63 a . . . insulating-member firstopening 63 b . . . third wall portion 63 c . . . fourth wall portion 63d . . . third connecting portion 63 e . . . fourth connecting portion 63f . . . fixing projection 63 f 1 . . . large-diameter portion 63 g . . .displacement prevention projection 63 h . . . lug portion 63 y . . .insulating-member second region 63 i . . . insulating-member secondopening 63 k . . . insulating-member annular rib 63 z . . .insulating-member third region 80 . . . cover 80 a . . . cover mainportion 80 b . . . arm portion 80 c . . . connecting projection 80 d . .. base opening 80 e . . . cover wall portion 80 f . . . wall portionopening 81 . . . cover 81 a . . . cover main portion 81 b . . . armportion 81 d . . . base opening 81 e . . . cover wall portion 81 f . . .wall portion opening 81 x . . . cover opening 90 . . . welded connectingportion 102 . . . sealing plate 102 x . . . pressing projection 161 . .. conductive member

The invention claimed is:
 1. A secondary battery comprising: anelectrode assembly including a positive electrode plate and a negativeelectrode plate; an exterior body having an opening and containing theelectrode assembly; a sealing plate configured to seal the opening; aconductive member having an opening portion at a side facing theelectrode assembly and disposed near a side of the sealing plate facingthe electrode assembly such that a first insulating member is disposedbetween the sealing plate and the conductive member; a deformation platethat seals the opening portion and is configured to deform in responseto an increase in a pressure in the exterior body; a current collectingmember that electrically connects the positive electrode plate or thenegative electrode plate to the deformation plate; and a terminal thatis electrically connected to the positive electrode plate or thenegative electrode plate via the current collecting member, thedeformation plate, and the conductive member; wherein the terminal isinserted through a terminal attachment hole in the sealing plate, aterminal-receiving hole in the first insulating member, and aterminal-receiving hole in tire conductive member and is connected tothe conductive member, wherein at least one of the conductive member andthe sealing plate has a pressing projection that projects toward thefirst insulating member from a portion thereof that faces the firstinsulating member, and wherein a conductive path between the positiveelectrode plate and the terminal or between the negative electrode plateand the terminal is broken in response to a deformation of thedeformation plate, wherein the first insulating member includes a firstgroove and a second groove in a portion thereof between the sealingplate and the conductive member at a position further away from theterminal-receiving hole in the first insulating member than a portionthereof that is pressed by the pressing projection, wherein the firstgroove is provided in a surface of the first insulating member thatfaces one of the sealing plate and the conductive member, and whereinthe second groove is provided in a surface of the first insulatingmember that faces other one of the sealing plate and the conductivemember.
 2. The secondary battery according to claim 1, wherein theterminal is crimped onto the conductive member.
 3. The secondary batteryaccording to claim 1, wherein the terminal is connected to theconductive member by welding.
 4. The secondary battery according toclaim 1, wherein the first insulating member includes a first groove ina portion thereof between the sealing plate and the conductive member ata position further away from the terminal-receiving hole in the firstinsulating member than a portion thereof that is pressed by the pressingprojection.
 5. The secondary battery according to claim 1, wherein thesecond groove is at a position further away from the terminal-receivinghole in the first insulating member than the first groove is.
 6. Thesecondary battery according to claim 1, wherein the first groove and thesecond groove are formed such that the first groove and the secondgroove partially overlap in plan view of the first insulating member. 7.The secondary battery according to claim 1, wherein the pressingprojection is provided on the conductive member.
 8. The secondarybattery according to claim 7, wherein the conductive member includes aconductive-member base portion arranged to face the sealing plate and atubular portion that extends from the conductive-member base portiontoward the electrode assembly, and wherein the pressing projection isprovided on the conductive-member base portion.